1. Field of the Invention
The present invention relates to an electronic integrating meter for totalizing electric energy, gas, water or other utility consumed over a period of time, and more particularly to such an electronic integrating meter for computing the quantity of utility being measured through digital processing.
2. Description of the Prior Art
Conventional integrating meters for totalizing a consumed quantity, such as of water, gas, or electrical energy, comprise a drive detection circuit for detecting the consumed quantity through revolution of a rotor such as a vane wheel, a converter circuit for converting an output signal from the drive detection circuit into a numerical value corresponding to the quantity consumed, a counter circuit for counting the output signals issued from the converter circuit, and a display circuit for enabling a display device to indicate an output from the counter circuit.
With the prior integrating meters thus constructed, weighting needs to be effected in the converter circuit dependent on the purpose for which the meter is used. For example, where the integrating meter is used for measuring the amount of water consumed, it is necessary for the converter circuit to be preset as to the number of liters of water indicated by one revolution of the vane wheel. The converter circuit may be weighted by using either switches and wires connected exteriorly to the electronic converter circuit, by the installation of a ROM (Read Only Memory) in the converter circuit. When switches are used, weighting of the converter can readily be changed, but the converter needs to be provided with terminals for reading out data from the switches, an arrangement which has prevented the meter from being made smaller in size.
It is necessary for such a water-measuring meter, for example, to detect the number of revolutions of the vane wheel to a nicety for the correct measurement of the amount of water used. To this end, the meter conventionally includes a magneto-resistive element (hereinafter referred to as "MR element") to which a constant voltage is applied and which has a resistance variable as the direction of a magnetic field changes which field is generated by a magnet rotated by the vane wheel. A change in the resistance of the MR element is detected as an output voltage signal which is supplied to one terminal of a comparator in which this output signal is compared with a reference voltage applied to another input terminal thereof, and the comparator produces a pulsed output signal.
Since the output signal from the MR element is a weak analog signal, the correct number of revolutions of the vane wheel cannot be detected when the comparator has a large offset or the reference voltage applied for comparison is unstable. The output characteristics of the comparator change to a large degree, resulting in a greater tendency to malfunction, especially when the meter is subject to large changes in the ambient temperature. A circuit which processes both analog and digital signals i.e., a hybrid functional circuit, cannot be integrated simply so as to obtain a one-chip integrated circuit. Such a circuit, therefore, is composed of a large number of parts which tend to lower reliability of the circuit in operation.